溅射NiCrAlY涂层氧化过程Al_2O_3膜结构与形貌的转变

PHASE AND MORPHOLOGY TRANSFORMATION OF Al_2O_3 DURING OXIDATION OF SPUTTERED NiCrAlY COATINGS

对溅射NiCrAlY涂层进行了 90 0℃ ,10 0 0℃ ,110 0℃空气中高温氧化。实验表明 ,氧化初期生成快速长大的亚稳态θ -Al2 O3 相 ,随着氧化时间延长 ,θ-Al2 O3 逐渐转变成α -Al2 O3 ,氧化动力学抛物线常数kp 也随之下降。θ→α -Al2 O3 相变速度与温度有关 ,温度越高 ,相变越快。对涂层进行真空热处理可促进θ→α -Al2 O3 转变 ,使涂层表面快速形成保护性能优异的α-Al2 O3 。

The isothermal oxidation of sputtered NiCrAlY coatings was performed in air at 900℃,1000℃ and 1100℃.Transient alumina θ-Al 2O 3,with fast growing rate,was formed on the surface of the coatings in the initial stage of oxidation.With oxidation time increasing,θ-Al 2O 3 transformed into α-Al 2O 3,and hence the parabolic rate constant decreased.The higher the temperature,the faster the transformation of θ-Al 2O 3 into α-Al 2O 3.A pre-heat treatment of the sputtered NiCrAlY coatings in vacuum can accelerate the transformation of θ-Al 2O 3 into α-Al 2O 3,and there with the protective α-Al 2O 3 scale is formed more rapidly on the surface of the coatings.